1. Field of the Invention
The invention relates to control relating to display of a display apparatus.
2. Description of the Background Art
When external light is incident on a display of a display apparatus, visibility of the display apparatus may be reduced depending on illuminance by the external light. Therefore, various technologies have been conventionally proposed to adjust a displaying state of the display apparatus in accordance with the illuminance by the external light.
For example, when the external light is dark like at night, a screen of the display apparatus is too bright for a user because the screen is much brighter as compared to surrounding environment, and the visibility of the screen of the display apparatus is reduced. Therefore, a technology that reduces an amount of light (light amount) of a backlight of the display apparatus when the illuminance by the external light is relatively low, in accordance with the low illuminance, and that reduces brightness of the screen of the display apparatus, has been conventionally known.
On the other hand, when incident external light is bright such as when direct sunlight or the like is incident, tones of displayed images are reduced due to, for example, reflection of the incident external light. Thus, the visibility of the screen of the display apparatus is reduced. Therefore, a technology that corrects images to be displayed on the display apparatus and that improves the visibility of the images when the illuminance by the external light is relatively high, has been conventionally known.
When the technology mentioned above or the like that adjusts the displaying state of the display apparatus in accordance with the illuminance by the external light is adopted, it is required to acquire accurate illuminance by the external light. The screen of the display apparatus, such as a vehicle-mounted display apparatus, used at various times of a day at various places is exposed to various types of light, such as a street light and sunlight. Therefore, a light sensor is required to detect a wide range of illuminance from very low illuminance of approximately 5 lx (equivalent to illuminance in a vehicle cabin at night, etc.) to very high illuminance of approximately 100,000 lx (equivalent to illuminance by direct sunlight in a daytime, etc.).
However, when an adopted relatively-low sensitivity light sensor is operable to detect illuminance in a range, for example, from 0 lx to 100,000 lx and indicates a detection result in 8 bits (0 to 255), the sensor cannot accurately detect low illuminance of approximately 5 lx because a resolution is too low. On the other hand, when an adopted relatively-high sensitivity light sensor is operable to detect illuminance in a range, for example, from 0 lx to 100 lx, the sensor cannot accurately detect illuminance exceeding 100 lx because the detection result overflows.
Therefore, a light sensor that is operable to switch detection sensitivities by switching values of resistors connected to a light receiving element has been conventionally proposed. Such a light sensor is operable to detect illuminance in a wide range by switching detection sensitivity modes in accordance with the illuminance detected.
However, when the illuminance by the external light changes significantly, such a light sensor needs to detect the illuminance, to switch detection sensitivity modes based on the illuminance detected and to detect the illuminance again based on a mode to which the detection sensitivity is switched. Thus, the light sensor requires some time to acquire accurate illuminance by the external light. Therefore, in a case where the displaying state of the display apparatus is adjusted based on the detection result of the light sensor, the displaying state of the display apparatus cannot be speedily adjusted responding to significant and frequent changes of the illuminance by the external light (e.g., when a display apparatus installed on a vehicle running at night receives bright light of street lights intermittently). As a result, the visibility of the display apparatus may be reduced.